JP7177723B2 - Preload adjustable spindle unit - Google Patents

Description

The present invention relates to a spindle unit for a machine tool, and more particularly, a spindle that ensures rigidity during low-speed rotation, prevents excessive preload during high-speed rotation, and prevents rigidity changes and accuracy deterioration due to bearing heat generation. regarding the unit.

As is well known, the spindle of a machine tool is generally rotatably supported in a housing by an angular contact ball bearing. Preload is applied to the bearing.

Methods for preloading angular contact ball bearings include a constant pressure preload method using springs and the like, and a fixed position preload method that adjusts the amount of preload by adjusting the width of a spacer placed between the angular contact ball bearings. In the constant pressure preload method, a constant preload is applied by a spring both during high-speed rotation and low-speed rotation.

However, with the constant pressure preloading method, it is difficult to ensure high rigidity like an appropriate fixed position preloading, and it has been pointed out that the structure is vulnerable to cutting vibration. For the same bearing, fixed position preloading has the advantage of higher stiffness compared to constant pressure preloading.

On the other hand, with fixed position preloading, if the initial preload is set low to suit high-speed rotation, the preload will be high at high-speed rotation, resulting in an optimal preload, but at low-speed rotation, the preload will be insufficient. There is a problem that the necessary rigidity cannot be obtained due to looseness. Conversely, if the initial preload is set high for low speed rotation, excessive preload will occur at high speed rotation, causing temperature rise and seizure. There is a problem that it is lost.

In addition, in machine tools, the rotation speed of the main shaft can be selected within a wide range depending on the machining conditions, so it is necessary to adjust the preload in accordance with the rotation speed of the main shaft. For this reason, in the past, the preload was adjusted according to the number of rotations of the spindle, and an adjustment method was used to ensure the optimum preload for the number of rotations of the spindle, to ensure rigidity during low-speed rotation, and to prevent excessive preload at high-speed rotation. has been proposed.

JP 2017-2975 A JP 2006-64127 A JP-A-2002-54631 JP-A-6-341431

However, none of these methods can ensure rigidity during low-speed rotation, prevent excessive preload during high-speed rotation, and prevent changes in rigidity and deterioration of accuracy due to heat generation of the bearing. .

Therefore, the present invention provides a preload-adjustable spindle unit that can ensure rigidity during low-speed rotation, does not become excessively preloaded during high-speed rotation, and can prevent changes in rigidity and deterioration of accuracy due to heat generation of the bearings. The challenge is to provide

The preload-adjustable spindle unit of the present invention is
A preload adjustable spindle unit for rotatably supporting the spindle of a machine tool in a housing,
a main shaft rotatably supported in a housing by a pair of bearings;
an inner ring spacer arranged between the inner rings of the pair of bearings;
a pair of outer ring spacers of the same length arranged with a gap between the outer rings of the pair of bearings on opposing sides ;
a stopper integrated with the housing and protruding toward the inner ring spacer side at a location corresponding to the gap between the outer ring spacers on the inner peripheral side of the housing;
and a piston arranged outside the outer ring of each of the pair of bearings,
By applying pressure to the piston and moving the piston toward the outer ring spacer, the outer ring spacer is compressed in the axial direction of the main shaft, making it possible to adjust the preload.

In the preload adjustment type spindle unit of the present invention, a main shaft rotatably supported in a housing by a pair of bearings, an inner ring spacer disposed between the inner rings of the pair of bearings, and a gap between the outer rings of the pair of bearings are provided. A pair of outer ring spacers arranged side by side and a stopper arranged between the pair of outer ring spacers, a piston is arranged outside each outer ring of the pair of bearings, and pressure is applied to the piston to move the piston between the outer rings. By moving to the seat side, it is possible to compress the outer ring spacer in the axial direction of the main shaft and adjust the preload.

For this reason, the preload can be changed by adjusting the pressure applied to the piston, so it is possible to apply preload that matches the number of rotations of the spindle, ensuring rigidity during low-speed rotation, and preloading during high-speed rotation. It is possible to prevent the occurrence of temperature rise and burning by preventing excessive increase.

In addition, since a stopper is provided between the pair of outer ring spacers, even if pressure is applied to the piston to move the piston toward the outer ring spacer and compress the outer ring spacer in the axial direction of the main shaft, the main shaft will not move. It is possible to effectively prevent it from being lost.

FIG. 4 is a diagram for explaining an embodiment of the preload-adjustable spindle unit of the present invention, showing the structure along the longitudinal direction; FIG. 10 is a view for explaining another embodiment of the preload-adjustable spindle unit of the present invention, showing the structure along the longitudinal direction;

The preload adjustment type spindle unit of the present invention has a main shaft to which a tool or workpiece chuck is attached at the tip. are arranged one-to-one, such as one-to-one and two-to-two.

An inner ring spacer is arranged between the inner rings of the pair of bearings, and a pair of outer ring spacers of the same length are arranged between the outer rings of the pair of bearings with a gap on the sides facing each other. A stopper is integrally formed with the housing and protrudes toward the inner ring spacer at a portion corresponding to the gap between the outer ring spacers on the inner peripheral side of the housing.

Further, a piston is arranged outside the outer ring of each of the pair of bearings. By applying pressure to the piston and moving the piston toward the outer ring spacer, the outer ring spacer is compressed in the axial direction of the main shaft. , thereby making it possible to adjust the preload.

Here, the main shaft is provided with an axial cooling liquid conveying path through which the cooling liquid passes, and an outer ring side cooling liquid conveying path through which the cooling liquid is passed is provided inside the housing. The inner ring spacer is cooled by the cooling liquid supplied to the outer ring side cooling liquid conveying path, and the outer ring spacer is cooled by the cooling liquid supplied to the outer ring side cooling liquid conveying path. It is possible to prevent a situation in which the initial preload cannot be maintained due to thermal expansion.

An embodiment of a preload-adjustable spindle unit (hereinafter simply referred to as "spindle unit") of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view for explaining the spindle unit of this embodiment. , and in the figure, 1 is the principal axis. That is, the spindle unit of this embodiment has a main shaft 1 which is rotatably supported on the inner peripheral side of a housing 2 and is rotated by a motor 14 . When cutting metal or the like, a cutting tool or a workpiece chuck is attached to the tip of the spindle 1 .

Next, in the figure, 3 and 4 are bearings for rotatably supporting the main shaft 1 in the housing 2. In this embodiment, angular contact ball bearings are used. are used so that their back surfaces face each other, and the pair of angular contact ball bearings 3 and 4 are arranged on the tip end side of the main shaft 1 with a space therebetween, so that the tip end of the main shaft 1 is side is rotatably supported on the inner peripheral side of the housing 2 . Angular contact ball bearings are well known and will not be described in detail. are partially fitted in grooves formed in the inner ring 9 and the outer ring 10, respectively. In addition, in the present embodiment, the angular contact ball bearings 3 and 4 are arranged one each. Therefore, two each of the front and rear angular contact ball bearings 3 and 4 may be provided.

Next, in FIG. 8, reference numeral 8 denotes an inner ring spacer arranged between the inner rings 10 of the pair of angular ball bearings 3,4. That is, in this embodiment, the pair of angular contact ball bearings 3 and 4 are arranged such that the respective inner rings 10 face each other with the inner ring spacer 8 interposed therebetween. Concatenated.

Next, in the figure, 7 is an outer ring spacer. That is, in the spindle unit of this embodiment, an outer ring spacer 7 is arranged between the outer rings 9 of the pair of angular contact ball bearings 3 and 4 .

In this embodiment, two outer ring spacers 7 having the same length are used, and the two outer ring spacers 7 are arranged on opposite sides with a gap 12 therebetween. there is That is, in this embodiment, the distance between the outer rings 9 of the angular ball bearings 3 and 4 is the length of the two outer ring spacers 7 plus the gap 12 between the outer ring spacers 7 .

On the other hand, on the inner peripheral side of the housing 2, a stopper 13 protrudes toward the inner ring spacer 8 at a location corresponding to the gap 12 between the outer ring spacers 7. The stopper 13 is attached to the outer ring spacer. It is inserted into the gap 12 between the two outer ring spacers 7 to fix the positions of the two outer ring spacers 7 . That is, the spindle unit of this embodiment employs a fixed-position preloading method, thereby increasing the rigidity as compared with the case where a constant-pressure preloading is employed.

Next, in the figure, 5 and 6 are pistons. That is, in this embodiment, the pistons 5 and 6 are arranged outside the respective outer rings 9 of the pair of angular contact ball bearings 3 and 4, and the pistons 5 and 6 are movable in the axial direction of the main shaft 1. and That is, a piston accommodating space is formed outside the outer ring 9 of each of the pair of angular contact ball bearings 3 and 4, and the pistons 5 and 6 are accommodated in the piston accommodating space so as to be movable in the axial direction of the main shaft 1. By moving the pistons 5 and 6 toward the outer ring 9 side, the outer ring spacer 7 can be compressed.

On the other hand, a pressure medium supply path 15 is formed in the housing 2, and the base end of the pressure medium supply path 15 is opened to the outside to form an injection port 15c.

The pressure medium supply path 15 is branched into two on the way, one 15a is connected to a piston accommodating space formed outside the outer ring 9 of the front angular ball bearing 3, and the other 15b is connected to the rear angular ball. It is connected to a piston housing space formed outside the outer ring 9 of the bearing 4 .

By supplying air or liquid into the pressure medium supply passage 15 and applying hydraulic or pneumatic pressure to the pistons 5 and 6, the pistons 5 and 6 are moved toward the outer ring 9, thereby 7 is compressed, the outer ring 9 of the angular contact ball bearing is moved toward the outer ring spacer 7, thereby making it possible to adjust the preload applied to the angular contact ball bearings 3 and 4.

That is, as is well known, in angular contact ball bearings, the straight line that connects the points of contact of the inner ring, the balls, and the outer ring has a contact angle with respect to the radial direction. When it rotates, the ball moves inward and the preload becomes excessive, and in some cases, the ball may come off the groove of the outer ring and ride on the shoulder of the groove.

Therefore, in the spindle unit of this embodiment, when the ball 11 moves toward the outer ring spacer 7 due to the centrifugal force during high-speed rotation, and excessive preload occurs, air or liquid may enter the pressure medium supply path 15. is supplied to apply hydraulic pressure or pneumatic pressure to the pistons 5 and 6 to move the pistons 5 and 6 toward the outer ring spacer 7 side, thereby adjusting the preload and preventing excessive preload. At this time, in the spindle unit of this embodiment, two outer ring spacers 7 are used, and the stopper 13 is arranged between each outer ring spacer 7. is compressed, the preload is not biased, and therefore it is possible to prevent the main shaft 1 from moving.

Thus, in the spindle unit of this embodiment, the pistons 5 and 6 are arranged outside the outer rings 9 of the pair of angular contact ball bearings 3 and 4, respectively, and the pistons 5 and 6 are moved by applying hydraulic pressure or air pressure to the pistons 5 and 6. , 6 toward the outer ring spacer 7, the preload can be adjusted. In the figure, 16 is an air vent, and 17 is an opening. That is, in this embodiment, when the pistons 5 and 6 are pushed by hydraulic or pneumatic pressure, and when the pistons 5 and 6 are returned by the extension force of the outer ring spacer when the hydraulic or pneumatic pressure is released. An air vent 16 and an opening 17 are formed in the housing 2 in order to prevent air from being trapped and allow the pistons 5, 6 to move smoothly.

By the way, as described above, in the spindle unit of this embodiment, the preload can be adjusted by applying hydraulic or pneumatic pressure to the pistons 5 and 6 to move the pistons 5 and 6 toward the outer ring spacer 7 side. , the preload of the angular contact ball bearing changes due to thermal expansion of the outer ring spacer 7 and the inner ring spacer 8 due to heat generated by rotation.

Therefore, in the spindle unit of this embodiment, the cooling liquid is supplied to the outer ring spacer 7 and the inner ring spacer 8, and the cooling liquid is also supplied to the inside of the main shaft, so that the outer ring spacer 7 and the inner ring spacer By maintaining the temperature of 8 at the initial temperature, the initial preload state can be maintained.

This structure will be explained with reference to FIG. 2. FIG. 2 is a partial cross-sectional view for explaining the method of supplying the cooling liquid in the spindle unit of this embodiment. The figure shows the configuration of FIG. 1 with a cooling liquid conveying path added, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the figure, reference numeral 21 denotes a shaft center side coolant supply passage for cooling the spindle. That is, in this embodiment, the spindle 1 has a core-side coolant supply path 21 inside, and the spindle 1 is cooled by supplying the coolant to the core-side coolant supply path 21 . making it possible to

Here, the shaft core side cooling liquid supply passage 21 will be described. The liquid supply path 21 extends to the vicinity of the tip portion of the main shaft 1 on the front end side and extends to the rear side of the main shaft 1 on the base end side. The rear end portion is connected to a cooling liquid supply means (not shown) such as a hose, so that cooling liquid can be supplied from the base end side of the core side cooling liquid supply passage 21 .

On the other hand, a core-side cooling liquid drainage channel 22 is formed around the core-side cooling liquid supply channel 21 , and the core-side cooling liquid drainage channel 22 extends to the vicinity of the tip of the main shaft 1 . In addition, the tip end portion is connected to the tip end portion of the shaft core side cooling liquid supply passage 21, and the base end portion is extended to the rear side of the main shaft 1 like the shaft core side cooling liquid supply passage 21 to drain water. Means (not shown) are connected. As a result, the coolant supplied to the shaft core side coolant supply passage 21 can be drained from the shaft core side coolant drain passage 22 . That is, in this embodiment, the core-side coolant supply path 21 and the core-side coolant drain path 22 form the core-side coolant transport path.

Therefore, in the spindle unit of this embodiment, as indicated by the arrow, the cooling liquid is supplied from the core side cooling liquid supply passage 21, and the supplied cooling liquid is drained from the shaft core side cooling liquid drainage passage 22. That is, it is possible to prevent the inner ring spacer 8 from thermally expanding by cooling the inner ring spacer 8 by passing the cooling liquid through the shaft core side cooling liquid conveying path.

Next, in the figure, 23 is an outer ring side coolant supply passage. That is, in the spindle unit of this embodiment, the outer ring side coolant supply path 23 is provided around the outer ring spacer 7, and the outer ring spacer 7 is cooled by passing the coolant through the outer ring side coolant supply path 23. , thermal expansion of the outer ring spacer 7 is prevented, and the outer ring spacer 7 and the inner ring spacer 8 are maintained at the same temperature.

Here, the outer ring side cooling liquid supply passage 23 will be described. In this embodiment, an outer ring side cooling liquid injection passage 24 is formed in the housing 2. A cooling liquid supply path 23 is connected. A cooling liquid supply means (not shown) such as a hose is connected to the base end of the outer ring side cooling liquid injection passage 24, thereby supplying cooling liquid to the outer ring side cooling liquid injection passage 24. By doing so, the cooling liquid is passed through the outer ring side cooling liquid supply passage 23 to cool the outer ring spacer 7, prevent the thermal expansion of the outer ring spacer 7, and keep the outer ring spacer 7 and the inner ring spacer 8 from The temperature is to be maintained.

Next, reference numerals 25 and 26 in the figure denote outer ring side cooling liquid drainage passages. That is, in this embodiment, a first outer ring side cooling liquid drainage path 25 is formed on the outer peripheral side of the housing 2, and the first outer ring side cooling liquid drainage path 25 is connected by the drainage port A to the above-mentioned It is connected to the tip side of the outer ring side coolant supply passage 23 .

Further, a second outer ring side cooling liquid drainage path 26 is formed in the housing 2, and the second outer ring side cooling liquid drainage path 26 is connected to the first outer ring side cooling liquid by a drainage port B. It is connected to the liquid drainage channel 25, and the other end is extended to the rear side of the housing 2 and connected to drainage means (not shown). Thereby, the cooling liquid is supplied to the outer peripheral side of the outer ring spacer 7 and the supplied cooling liquid can be discharged to the outside of the housing 2 . That is, in this embodiment, the outer ring side coolant supply path 24, the outer ring side coolant supply path 23, and the first and second outer ring side coolant drain paths 25 and 26 form an outer ring side coolant transfer path. ing.

Here, to briefly explain the flow of the cooling liquid for cooling the outer ring spacer 7, the cooling liquid supplied from the outer ring side cooling liquid injection passage 24 into the housing 2 flows as indicated by the arrows. By passing through the liquid supply path 23 , the outer ring spacer 7 is cooled through the outside of the outer ring spacer 7 .

Next, the coolant that has cooled the outer ring spacer 7 by passing outside the outer ring spacer 7 passes through the drain port A and is discharged to the first outer ring side coolant drain passage 25 as indicated by the arrow. Further, it is drained to the second outer ring side coolant drain passage 26 through the drain port B, and then to the outside of the housing 2 .

Therefore, in the spindle unit of this embodiment, the cooling liquid is supplied from the outer ring side cooling liquid injection passage 24 and the outer ring side cooling liquid supply passage 23, and the supplied cooling liquid is discharged from the outer ring side cooling liquid drainage passages 25 and 26. Thus, it is possible to cool the outer ring spacer 7 and prevent the outer ring spacer 7 from thermally expanding.

Therefore, in the spindle unit of this embodiment, it is possible to prevent the inner ring spacer 8 and the outer ring spacer 7 from thermally expanding due to the heat generated by the angular contact ball bearing. 21 cools the inner ring spacer 8, and the outer ring side coolant supply passage 23 cools the outer ring spacer 7, thereby maintaining the temperature of the outer ring spacer 7 and the inner ring spacer 8 at the same temperature. In addition, it is possible to prevent the outer ring spacer 7 and the inner ring spacer 8 from expanding individually, so that the initial preload state can be reliably maintained.

In this way, in the spindle unit of this embodiment, the pistons 5 and 6 are arranged outside (on the side opposite to the stopper) of the pair of outer ring spacers 7 arranged with the stopper 13 interposed therebetween. By moving the pistons 5 and 6 toward the outer ring spacer 7 side by adding By controlling , it is possible to apply a preload that matches the number of revolutions of the spindle 1, to ensure rigidity during low-speed revolution, and to prevent excessive preload during high-speed revolution to prevent temperature rise and seizure. It is possible. At this time, in the spindle unit of this embodiment, since the stopper 13 is provided between the pair of outer ring spacers 7, pressure is applied to the pistons 5 and 6 to move the pistons 5 and 6 toward the outer ring spacer 7 side. Even when the outer ring spacer 7 is compressed in the axial direction of the main shaft 1, the preload is not biased and the main shaft 1 can be prevented from moving.

Furthermore, the spindle unit of this embodiment has a core-side cooling liquid supply passage 21 for cooling the inner ring spacer 8 and an outer ring-side cooling liquid supply passage 23 for cooling the outer ring spacer 7. Therefore, it is possible to reliably prevent the outer ring spacer 7 and the inner ring spacer 8 from expanding due to the heat generated by the rotation of the angular contact ball bearing, thereby reliably maintaining the initial preload state. be.

INDUSTRIAL APPLICABILITY The spindle unit of the present invention can maintain the initial preload of the angular contact ball bearing that rotatably supports the main shaft of the machine tool. be.

1 main shaft 2 housing 3 front angular contact ball bearing 4 rear angular contact ball bearing 5 front piston 6 rear piston 7 outer ring spacer 8 inner ring spacer 9 outer ring of angular contact ball bearing 10 inner ring of angular contact ball bearing 11 ball of inner ring of angular contact ball bearing 12 Gap between outer spacers 13 Stopper 14 Motor 15 Pressure medium supply path 16 Air vent 17 Release port 21 Shaft core side coolant supply path 22 Shaft side coolant drain path 23 Outer ring side coolant supply path 24 Outer ring side coolant Injection passage 25 First outer ring side cooling liquid drainage passage 26 Second outer ring side cooling liquid drainage passage B
A, B drain

Claims (3)

A preload adjustable spindle unit for rotatably supporting the spindle of a machine tool in a housing,
a main shaft (1) rotatably supported in a housing (2) by a pair of bearings (3, 4);
an inner ring spacer (8) arranged between the inner rings (10) of the pair of bearings (3, 4);
a pair of outer ring spacers (7) of the same length arranged with a gap (12) between the outer rings (9) of the pair of bearings (3, 4) on the sides facing each other ;
A stopper (13) integral with the housing protrudes toward the inner ring spacer (8) at a location corresponding to the gap (12) between the outer ring spacers (7) on the inner peripheral side of the housing (2). When,
Pistons (5, 6) integral with the housing and arranged outside respective outer rings (9) of the pair of bearings (3, 4),
By applying pressure to the pistons (5, 6) and moving the pistons (5, 6) toward the outer ring spacer (7), the outer ring spacer (7) is compressed in the axial direction of the main shaft (1). A preload adjustment type spindle unit characterized in that the preload can be adjusted by 2. Preload adjustable spindle unit according to claim 1, characterized in that the bearings (3, 4) are angular contact ball bearings. An axial center side cooling liquid conveying path for passing the cooling liquid inside the main shaft (1) and an outer ring side cooling liquid conveying path for passing the cooling liquid around the outer ring spacer (7), The inner ring spacer (8) is cooled by the cooling liquid passing through the shaft center side cooling liquid conveying path, and the outer ring spacer (7) is cooled by the cooling liquid passing through the outer ring side cooling liquid conveying path. 3. The preload adjustment type spindle unit according to claim 1 or 2.

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